This invention relates to a variable roller valve system for use in an internal combustion engine. A traditional feature of such engines is that the apertures and the relative timing of the intake and exhaust valves remain fixed during operation according to pre-adjusted settings. It is well recognized in the art, however, that dynamic control over intake and exhaust flow is required to optimize combustion efficiency and minimize noxious exhaust emissions over a range of operating speeds and power demands. The present invention provides this dynamic control.
The present invention achieves this dynamic control by improving on a basic rotary valve design. A Sliding Iris.TM. feature provides separate, independent, and continuous control over the aperture sizes of the intake ports and the exhaust ports while the engine is running. At the same time, and also while the engine is running, hydraulic mechanisms provide similar separate, independent and continuous control over the relative timing phases of the intake valve train and the exhaust valve train with respect to the crankshaft.
The result is unprecedented control over the combustion efficiency of the engine. A conventional control means, such as a computer, receives information from the operator, from the engine's environment, and from the engine itself. The control means then interprets the data received and instructs the present invention to adjust for optimum fuel flow and valve phase according to current operating conditions. With proper calibration, optimum combustion conditions can thus be maintained as the engine is operated through varying speeds, load demands and temperatures. This control over combustion provides a significant improvement in efficiency through the widest possible range of engine speeds and load demands, as well as a dramatic reduction in exhaust gas impurities.
The use of roller valves to gain dynamic control over intake/exhaust flow and valve phase is known in the art. Previous inventions have sought to vary roller valve port apertures by circumferential displacement of inner and outer members. Such inventions require elaborate control mechanisms, and potentially disrupt engine timing by altering valve duration. For example, Conklin, U.S. Pat. No. 5,205,251, discloses sleeves over solid rollers constricting valve apertures through relative circumferential displacement. Conklin does not disclose, however, how this displacement is physically actuated or synchronized with crankshaft rotation. Rus et al., U.S. Pat. No. 4,481,917, discloses coaxial annular shutter assemblies, one assembly rotating around the top of each cylinder about the cylinder's own axis. Rus requires a complex gearing mechanism to synchronize the independent operation of the two rotating valve members above each cylinder. Further, both these inventions alter valve duration as the valve port apertures are circumferentially constricted.
In contrast, the present invention's Sliding Iris.TM. feature varies valve port apertures through longitudinal displacement of inner and outer members. This improves on the prior art by simplifying the required control mechanism and by constricting valve port aperture without altering duration.
A further novel feature of this design is the dynamic seal used to enclose the cylinder cavity more tightly during the compression and power strokes. A pressure take-off from the inside of the cylinder cavity allows cylinder pressure to tighten the rotary valve seal directly against the valve roller. This eliminates the potential for valve seal leakage during high pressure cylinder conditions. This dynamic seal process is also apparently unknown in the art.
The prior art typically specifies sealing arrangements either as a function of close component tolerance, such as in Pizzicara, U.S. Pat. No. 4,920,984, or as a function of multi-component seals under constant mechanical spring pressure, such as in Place, U.S. Pat. No. 5,095,870. Both of the seal arrangements disclosed in these inventions are prone to gas blow-by and do not improve on the seal that would be provided by traditional "popper" valves.
The present invention's dynamic seal feature borrows from traditional "popper" valves and improves on the prior art by using cylinder pressure itself to tighten the seal positively during compression and power strokes. Further, potential seal wear is reduced as pressure against the seal is reduced during intake and exhaust strokes.